I love alternate R.A.B. theories. Everyone, including me, was instantly convinced it was Regulus. There are a couple things, though.

Just because Sirius thought Regulus was weak doesn't mean he was. Also, Borgin hasn't exactly appeared to be very brave either. The way he cows before the Malfoys sort of neutralizes your strength of character arguments.

Also, what about the locket in Grimmauld Place? It could certainly be a red herring, and I could certainly see Borgin wanting his Slytherin locket back, but still...

Then you told me, two years later, that on the night that Voldemort returned to his body, he made a most illuminating and alarming statement to his Death Eaters. "I, who have gone further than anybody along the path that leads to immortality." That was what you told me he said. "Further than anybody." And thought I knew what that meant, though the Death Eaters did not.

The DE don't know much about VM secrets, maybe he told some of them about making a Horcrux (maybe some were around) but none of them knows more then one Horcrux. Regulus Black was a young DE and probably he wasn't among that trustworthy DE's (and he was to young to be there for long). In conclusion Regulus could be a DE and not knowing about the Horcruxes. (it sounds as he would only know about one Horcrux, because he hoped that VM will be mortal again, after he destroyed it)

__________________The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts. (Bertrand Russell)

A very good editorial. But it wasn't that convincing to me (sorry!) I know I can't put your theory to rest because everything is a possiblility. I just don't think it can be Regalus, like you said. It's just too easy of an answer. J.K. Rowling doesn't write her books in simplistic form.

Who says that R.A.B. has to be a guy? Is it me, or is it De ja Vue? Half-Blood Prince all over again! Aren't we all guessing?

Yea, I agree tht Regulus Black is a red herring & Borgins a good theory but in the note it kinda sounded like the person was dying. Unless Burke & Borgin took polyjuice potion & pretended they were each other, maybe one of them was mor valuable than the other or somthing? They did need 2 people 2 get past the obstacles. Thats a bit far fetched tho.

I thought of Borgin as well, but I just can't figure how he would know about Voldy's fave cave. Someone who knows their potions would be likely, I think. Anyone fit that description with corresponding initials?

Yes this is a good theory.
This might be a stupid theory but Ollivander dissapeared during the holidays, which was about the same time we last saw Borgin. Maybe they went together? Borgin would have needed an accomplice to either drink the stuff or force it down borgins throat. There was no struggle at Ollivanders place, so you never know...

Very well written editorial, and I am glad other people are thinking of all the possibilities!

But I don't think that Borgin is exactly how you descibed him. I think he fears and is perhaps jealous of all the power that Death Eaters have, or perhaps doesn't agree with their extreme views, but he's not completely against them, as we can see that families such as the Malfoy's make up quite a bit of his business.

ALso, he is clearly heavily involved in the dark arts, which is fishy to start off with.

I could also be completely wrong, but he seems quite a passive character, and less likely to be a disguised hero.

Regulus does seem to make more sense, in more ways than just his initials, but JK has comstantly proved that things are not always as they seem!!!

I agree that RAB is not Regulus Black, nor that it is a Death Eater. Because I also believe that there is no way Voldemort would be careless enough to drop that he had Horcruxes, or their location--Voldemort, who didn't even trust his own Death Eaters. He knew he had so many enemies, and that one of them could easily be spying on him. Voldemort is too careful, too chill (not in a good way), to let everyone know he had Horcruxes even when he was busy being arrogant and bragging about his achievements.

"I discovered your secret..." R.A.B must have been a very strong and intelligent wizard (witch?) if he could pass through all the barriers and come back out alive (although, perhaps, he died during the attempt and he knew he would, thus the line about "I will be dead long before you read this...") That's one reason I rule out Regulus (although we do see him through Sirius's eyes, which are more than just slightly biased), and also Borgin. We never see Borgin. A man like Borgin, partners with a man like Burke, who runs a store like Borgin & Burke in a place like Knockturn Alley, is not likely to be a particularly strong or "good" (as in fighting for the light) wizard. Rowling, however, is always full of surprises, and I must say even Borgin seems likelier than Regulus Black.

Might R.A.B be three people? Although it is written in the first person singular, and with one hand, and there are only initials....seemingly, it is only one person. But perhaps these three people were very close, similar to how close Sirius, James, and Lupin were at Hogwarts--close enough that they can talk about themselves, collectively, as "I." The "Dark Lord" salutation could have been mocking. They could easily have gotten one person to write the note. Think of it: a wizard as amazing as Dumbledore could not have gotten through without somebody else, even though Harry is still not fully grown; it would be extremely difficult, I should think, for a single wizard (likely not as great as Dumbledore) to get through and back. It would be so much easier for three people!

I think you did a lot of good research and thinking through this editorial, but I'm not entirely convinced it's not Regulus.

The most compelling evidence, besides the initials and his being a junior DE, is that the mysterious locket (so like Slytherin's) at Grimmauld Place, and this little "red herring" of ours shared a house. Now, I don't know about you, but I think that this is a large, and quite subtle clue. It's one of those "stroke of genius" conclusions we're all meant to eventually make, probably.

After my initial thougts about regulus, this is also what I came up with. I think that Borgin makes perfect sense. He might not be the most powerful wizard, but who know more about the dark art and dark arts artifact than him. Maybe LV and Snape, but no one else. Potions and Artifacts are both very subtle arts, something that you can practice behind the scenes. Maybe he has artifacts or a powerful vaccine to help him get past the draught of living death.

He also worked with LV when he was Tom Riddle, his background would have been much less taboo then and he could have found out about his orphanage. I can't remember the exact order of events, but Borgin likely would have recognized the Gaunt Ring for what it really was.

Being a previous employer of LV he was probably questioned by a slew of Aurors and Ministry people during the first war. A wizard with his saavy and knowledge of the Dark Arts could put the pieces together.